aop - Join Points in Aspect Oriented Programming -

i studying aop , important parts of advice, pointcuts, , join points. read understandable explanation advice , pointcuts links. aspect oriented programming vs. object-oriented programming

however, have difficulty understanding join points is. read, join points well-defined locations in structure of program aspect can weave in advice code.

but, when comes the real example, not find example understand example of join points.

as taken example in link above, if advice , poincuts written below, define join points?

classical approach:

void set...(...) {     :     :     display.update(); } 

advice:

after() : set() {    display.update(); } 

poincuts:

pointcut set() : execution(* set*(*) ) && this(mygraphicsclass) && within(com.company.*); 

void set...(...) is joinpoint

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as know aspect association of concern, pointcut , joinpoint

• the implementation of cross-cutting concern called concern.
• the defined location within class concern going attached joinpoint.
• the place joinpoint(s) specified, either through configuration or code, pointcut.

a concern important 1 or more stakeholders. additionally concerns can conceptually divided 2 categories (the implementation each can same):

a side effect: concern not changing behaviour @ joinpoint, instead introduces additional actions.

a logging concern example of side effect,

e.g. each call targeted method (this joinpoint) bankwithdrawalhandler.execute(icommand command) first call concern loggingconcern.execute(icommand command)

which able run before , after execute method, logging such things start time/end time/total time/in parameters/out parameters etc.

a side effect can:

• inspect/capture input parameters @ targeted pointcut required , action additional processing
• inspect/capture output result @ targeted pointcut required , action additional processing

an advice: concern potentially change input and/or output of targeted method.

a caching concern simple example - e.g. whenever run-time executes targeted method (this joinpoint) repository.find<t>(long id) method cacheconcern.find<t>(long id) configured run first , allow call continue on repository.find() method if value not found in cache.

an advice can:

• inspect input parameters @ targeted pointcut , modify them if needed
• cancel or avoid execution of targeted method , replace different implementation
• inspect output result of targeted method , modify or replace required

within .net there number of established techniques implementing pointcut:

• post build il weaving/postsharp
• dependency inversion (inversion of control (ioc) , dependency inversion (di))
• interception/dynamicproxy